The quality of PET images has improved in recent years with the introduction of new technologies that improve PET calibration and assure high image quality. Cylinder sources are widely used in PET calibration and image quality assurance procedures. For instance, some procedures are positioning sensitive with respect to crystal efficiency calibration and image quality at different positions of the scanner's field of view (FOV). One approach to address these issues is to determine the position of the cylinder source at a specific location in the FOV. Techniques to determine the position are external mechanical instruments such as lasers or by using imaging technologies such as CT or PET reconstruction to determine the position.
However, using external instruments have additional cost and require additional calibration procedures. Using a CT image may result in the misalignment between the PET scanner and the CT scanner, which affects the positioning accuracy. Finally, using a PET reconstructed image has a number of issued associated therewith. For example, the reconstructed image suffers from reconstruction artifacts if the system is not fully or properly calibrated. Examples include ring artifacts that occur if the intrinsic crystal efficiency and block profile effect correction is not applied. For the ease of notation, the term “crystal efficiency” corresponds to “intrinsic crystal efficiency and block profile effect” in the following disclosure. Another issue is that the PET reconstruction process is an iterative process that is time consuming and involves computational expensive physical corrections such as scatter estimation.